Heinz body hemolytic anemias result from the presence of unstable hemoglobin mutants or from the interaction of normal hemoglobin with certain drugs and chemical agents. Phenylhydrazine, one of the more active of these substances, has played a central role in the study of the hemolytic process. In preliminary work, we have discovered tha the green chromophore formed in the interaction of hemoglobin with phynyl-hydrazine is N-phenylheme. The purpose of this project is to determine the mechanism which results in alteration of the prosthetic heme and the role of N-phenylheme formation in the subsequent precipitation of hemoglobin as Heinz bodies. An investigation of the heme binding sites in serum hemoproteins using the regio- and stereoselectivity of adduct formation as a probe is planned. The structure of the prosthetic group in sulfhemoglobin, a defective hemoglobin found in patients treated with oxidative drugs or suffering from certain disorders, is to be elucidated. The prosthetic groups of other erythrocyte green hemoproteins are to be investigated. Chemical models for the reactions which convert hemoglobin heme to abnormal derivatives are to be developed. In addition to primary emphasis on the mechanisms of drug induced hemolytic anemia, the project is intended to explore the possible physiological generality and importance of reactions with prosthetic heme nitrogen atoms in hemoglobin.